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Complex I Inhibitor (complex + i_inhibitor)
Selected AbstractsCharacterization of depolarization and repolarization phases of mitochondrial membrane potential fluctuations induced by tetramethylrhodamine methyl ester photoactivationFEBS JOURNAL, Issue 7 2005Angela M. Falchi Depolarization and repolarization phases (D and R phases, respectively) of mitochondrial potential fluctuations induced by photoactivation of the fluorescent probe tetramethylrhodamine methyl ester (TMRM) were analyzed separately and investigated using specific inhibitors and substrates. The frequency of R phases was significantly inhibited by oligomycin and aurovertin (mitochondrial ATP synthase inhibitors), rotenone (mitochondrial complex I inhibitor) and iodoacetic acid (inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase). Succinic acid (mitochondrial complex II substrate, given in the permeable form of dimethyl ester) abolished the rotenone-induced inhibition of R phases. Taken together, these findings indicate that the activity of both respiratory chain and ATP synthase were required for the recovery of the mitochondrial potential. The frequency of D phases prevailed over that of R phases in all experimental conditions, resulting in a progressive depolarization of mitochondria accompanied by NAD(P)H oxidation and Ca2+ influx. D phases were not blocked by cyclosporin A (inhibitor of the permeability transition pore) or o -phenyl-EGTA (a Ca2+ chelator), suggesting that the permeability transition pore was not involved in mitochondrial potential fluctuations. [source] ETHANOL-INDUCED SUPEROXIDE RADICALS IN FETAL CORTICAL NEURONS: CELLULAR ROS NETWORKALCOHOLISM, Issue 2008Amina E Jamali Alcohol exposure to the developing brain compromises both neurons and glial functions. While neurons are considered the primary targets, microglia may play a neurotoxic role in this process. Previous studies demonstrated that neuron death is due to oxidative stress and mitochondrially mediated (Intrinsic). These studies showed a rapid increase (within minutes) in reactive oxygen species (ROS). Due to the diffusive nature of ethanol and multiple sources of free radicals, we sought to determine the primary source of superoxide targeted by ethanol. Confocal studies of neurons suggest that the superoxide radicals may originate from the mitochondria. Using whole neurons in a luminol-based chemiluminescence assay (Diogenes) we detected superoxide radicals in the extracellular mileu. We observed a two-three fold transient increase in the steady state generation of superoxide radicals between 20 minutes to one hour of ethanol exposure (4mg/ml). However, the presence of Rotenone (mitochondrial complex I inhibitor) and DPI (an inhibitor of all flavinoids) blocked the release of these superoxide radicals. Interestingly, cortical microglia treated identically with ethanol, showed a greater than five fold increase in superoxide generation with a maximum at one hour. Moreover, since ethanol is known to induce hydrogen peroxide generation, it was used as a mimetic. Hydrogen peroxide also induced the production of superoxide different time kinetics. Thus, together these data demonstrate that ethanol induces the steady state production of superoxide radicals in the extracellular mileu in a mitochondrial dependent manner. Since NOX2 an NADPH oxidase is expressed in neurons, it is a potential candidate for the secondary sites of superoxide generation. The ROS network between mitochondria and the plasma membrane highlights new therapeutical targets to counter ethanol toxicity. [source] Alterations of Mitochondria in Peripheral Blood Mononuclear Cells of Vitiligo PatientsPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2003Maria Lucia Dell'Anna The possible role for a defective mitochondrial functionality in the pathogenesis of vitiligo was investigated by measuring intracellular levels of reactive oxygen species and of antioxidants, the activity of Krebs cycle enzymes, as well as the effects of inhibitors of the electron transport chain, in peripheral blood mononuclear cells from patients with active or stable disease vs. normal subjects. Plasma glyoxal levels were also determined in the same groups of subjects as an index of systemic oxidative stress. In patients with vitiligo in active phase, we observed an increased intracellular production of reactive oxygen species with a consequent imbalance of the prooxidant/antioxidant equilibrium, whereas plasma did not show apparent alterations in glyoxal levels, ruling out a systemic oxidative stress. In patients with stable disease, the balance between pro-oxidants and anti-oxidants seems to be maintained. Moreover, a marked increase in the expression of mitochondrial malate dehydrogenase activity and a specific sensitivity to electron transport chain complex I inhibitor were observed. Overall, these data provide further evidence for an altered mitochondrial functionality in vitiligo patients. [source] Mitochondrial modulation of Ca2+ sparks and transient KCa currents in smooth muscle cells of rat cerebral arteriesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2004Serguei Y. Cheranov Mitochondria sequester and release calcium (Ca2+) and regulate intracellular Ca2+ concentration ([Ca2+]i) in eukaryotic cells. However, the regulation of different Ca2+ signalling modalities by mitochondria in smooth muscle cells is poorly understood. Here, we investigated the regulation of Ca2+ sparks, Ca2+ waves and global [Ca2+]i by mitochondria in cerebral artery smooth muscle cells. CCCP (a protonophore; 1 ,m) and rotenone (an electron transport chain complex I inhibitor; 10 ,m) depolarized mitochondria, reduced Ca2+ spark and wave frequency, and elevated global [Ca2+]i in smooth muscle cells of intact arteries. In voltage-clamped (,40 mV) cells, mitochondrial depolarization elevated global [Ca2+]i, reduced Ca2+ spark amplitude, spatial spread and the effective coupling of sparks to large-conductance Ca2+ -activated potassium (KCa) channels, and decreased transient KCa current frequency and amplitude. Inhibition of Ca2+ sparks and transient KCa currents by mitochondrial depolarization could not be explained by a decrease in intracellular ATP or a reduction in sarcoplasmic reticulum Ca2+ load, and occurred in the presence of diltiazem, a voltage-dependent Ca2+ channel blocker. Ru360 (10 ,m), a mitochondrial Ca2+ uptake blocker, and lonidamine (100 ,m), a permeability transition pore (PTP) opener, inhibited transient KCa currents similarly to mitochondrial depolarization. In contrast, CGP37157 (10 ,m), a mitochondrial Na+,Ca2+ exchange blocker, activated these events. The PTP blockers bongkrekic acid and cyclosporin A both reduced inhibition of transient KCa currents by mitochondrial depolarization. These results indicate that mitochondrial depolarization leads to a voltage-independent elevation in global [Ca2+]i and Ca2+ spark and transient KCa current inhibition. Data also suggest that mitochondrial depolarization inhibits Ca2+ sparks and transient KCa currents via PTP opening and a decrease in intramitochondrial [Ca2+]. [source] Activation of adenosine triphosphate-sensitive potassium channels confers protection against rotenone-induced cell death: Therapeutic implications for Parkinson's diseaseJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2002Kwok-Keung Tai Abstract It is anticipated that further understanding of the protective mechanism induced by ischemic preconditioning will improve prognosis for patients of ischemic injury. It is not known whether preconditioning exerts beneficial actions in neurodegenerative diseases, in which ischemic injury plays a causative role. Here we show that transient activation of ATP-sensitive potassium channels, a trigger in ischemic preconditioning signaling, confers protection in PC12 cells and SH-SY5Y cells against neurotoxic effect of rotenone and MPTP, mitochondrial complex I inhibitors that have been implicated in the pathogenesis of Parkinson's disease. The degree of protection is in proportion to the bouts of exposure to an ATP-sensitive potassium channel opener, a feature reminiscent of ischemic tolerance in vivo. Protection is sensitive to a protein synthesis inhibitor, indicating the involvement of de novo protein synthesis in the protective processes. Pretreatment of PC12 cells with preconditioning stimuli FeSO4 or xanthine/xanthine oxidase also confers protection against rotenone-induced cell death. Our results demonstrate for the first time the protective role of ATP-sensitive potassium channels in a dopaminergic neuronal cell line against rotenone-induced neurotoxicity and conceptually support the view that ischemic preconditioning-derived therapeutic strategies may have potential and feasibility in therapy for Parkinson's disease. © 2002 Wiley-Liss, Inc. [source] Apoptosis-inducing factor deficiency sensitizes dopaminergic neurons to parkinsonian neurotoxinsANNALS OF NEUROLOGY, Issue 2 2010Celine Perier PhD Objective Mitochondrial complex I deficits have long been associated with Parkinson disease (PD). However, it remains unknown whether such defects represent a primary event in dopaminergic neurodegeneration. Methods Apoptosis-inducing factor (AIF) is a mitochondrial protein that, independently of its proapoptotic properties, plays an essential physiologic role in maintaining a fully functional complex I. We used AIF-deficient harlequin (Hq) mice, which exhibit structural deficits in assembled complex I, to determine whether primary complex I defects linked to AIF depletion may cause dopaminergic neurodegeneration. Results Despite marked reductions in mitochondrial complex I protein levels, Hq mice did not display apparent alterations in the dopaminergic nigrostriatal system. However, these animals were much more susceptible to exogenous parkinsonian complex I inhibitors, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Subtoxic doses of MPTP, unable to cause damage to wild-type animals, produced marked nigrostriatal dopaminergic degeneration in Hq mice. This effect was associated with exacerbated complex I inhibition and increased production of mitochondrial-derived reactive oxygen species (ROS) in Hq brain mitochondria. The antioxidant superoxide dismutase-mimetic compound tempol was able to reverse the increased susceptibility of Hq mice to MPTP. Supporting an instrumental role for mitochondrial-derived ROS in PD-related neurodegeneration, transgenic mice overexpressing mitochondrially targeted catalase exhibited an attenuation of MPTP-induced mitochondrial ROS and dopaminergic cell death. Interpretation Structural complex I alterations linked to AIF deficiency do not cause dopaminergic neurodegeneration but increase the susceptibility of dopaminergic neurons to exogenous parkinsonian neurotoxins, reinforcing the concept that genetic and environmental factors may interact in a common molecular pathway to trigger PD. ANN NEUROL 2010;68:184,192 [source] | |||||||||||||